.box {
    display: grid;
    grid-template-columns: repeat(3, 1fr); /* 三列等宽 */
    grid-template-rows: repeat(3, 1fr);
    width: 300px;
    height: 300px;
    margin: 0 auto;
}
.grid-item {
    border: 1px solid #ccc;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 40px;
}
